The invention relates to traffic management in a packet data network having group transmission capability. A transmission group can be formed, for example, by broadcasting or multicasting an encrypted transmission signal and by distributing decryption keys only to the intended recipients (the group members). The packet data network is used for conveying several services to several subscribers. Some services are more popular than others.
The invention is especially applicable to a multi-bearer packet data network. A multi-bearer network, or an MBN, is a network having the capability to carry a data packet via one of several alternative bearers. To be more precise, the term ‘multi-bearer network’ should be interpreted as meaning ‘multi-bearer-type network’, or in other words, a network arrangement which provides multiple, different bearer types for data packet delivery. An example of a suitable MBN is a so-called MEMO concept (Multimedia Environment for Mobiles), see reference 1. Additionally, the MBN supports mobility of a subscriber terminal. An example of terminal mobility is IP mobility, which is the topic of standard RFC2002 by the Internet Engineering Task Force (IETF). This RFC standard is incorporated herein by reference.
The problem underlying the invention is how to optimize the use of transmission resources. This problem is most significant in a packet radio network, because radio bandwidth is a limited natural resource. Broadcast systems based on orthogonal frequency division multiplexing modulation (OFDM) and on single frequency network (SFN) techniques are very efficient when the same signal is distributed to a large group of subscribers.